Centrifugal actuator for limited slip differential

ABSTRACT

A LIMITED SLIP DIFFERENTIAL MECHANISM HAVING A NORMALLY DISENGAGED MAIN CLUTCH PRODUCING LOCK-UP WHEN ACTIVATED, WHICH IS OPERATED BY MEANS OF AN ACTUATOR DEVICE IN TURN ACTIVATED BY A PREDETERMINED LEVEL OF DIFFERENTIAL ACTION WHICH IS VARIED WITH THE RATE OF CHANGE OF LEVELS OF DIFFERENTIAL ACTION. THE ACTUATOR INCLUDES AN ACTUATOR MEMBER WHICH IS ROTATIONALLY DRIVEN BY DIFFERENTIAL ACTION AND UPON WHICH SPRING-BIASED CENTRIFUGAL WEIGHTS ARE PIVOTALLY MOUNTED AND ARRANGED SO THAT AT A PREDETERMINED VELOCITY AND ACCELERATION OF THE ACTUATOR MEMBER ONE OF THE WEIGHTS MOVE OUTWARDLY AND APPLIES A BRAKING FORCE TO THE ACTUATOR MEMBER INHIBITING ITS ROTATION. AN ARRANGEMENT IS PROVIDED FOR ACTUATION OF THE NORMALLY DISENGAGED MAIN CLUTCH IN RESPONSE TO THIS IBHIBITED ROTATION, SO THAT THE DIFFERENTIAL ACTION IS UNIHIBITED AT   LOW LEVELS OF DIFFERENTIAL ACTION. A HIGH ROAD SPEED CUTOUT OF THE ACTUATOR IS ALSO PROVIDED SO THAT NO LOCK-UP WILL OCCUR AT RELATIVELY HIGH ROAD SPEEDS.

y 1974 w. c. OTTEMANN Re. 28,004

CEN'I'RIFUGAL ACTUATOR FOR LIIITED SLIP DIFFERENTIAL 4 Sheets-Sheet 1Original Filed Sept. 17, 1969 M I/AZM 4. 32 6335471 y 7, 1974 w. c.OTTEMANN Re. 28,004

INVENTOR. M17247?! C Qifcmdrm 4770 FIVE) y 7, 1974 w. c. OTTEMANN Re.28,004

CENTRIFUGAL ACTUATOR FOR LIMITED SLIP DIFFERENTIAL Original Filed Sept.17, 1969 4 Sheets-Sheet 5 I mv NTOR. 14 1/1 42 C 02 6271472 /7 7 TOF/VEXy 7, 1974 w. c. OTTEMANN Re. 28,004

CENTRIFUGAL ACTUATOR FOR LIIITED SLIP DIFFERENTIAL Original Filed Sept.17, 1969 4 Sheets-Sheet 4 FEZLE.

I NVE TOR.

14 17/4 6: 0f chm/m E45- ffl? United States Patent 28,004 CENTRIFUGALACTUATOR FOR LIMITED SLIP DIFFERENTIAL William C. Ottemanu, Union Lake,Mich., assignor to Eaton Corporation, Cleveland, Ohio Original No.3,606,803, dated Sept. 21, 1971, Ser. No.

858,700, Sept. 17, 1969. Application for reissue June 7, 1973, Ser. No.367,860

Int. Cl. F16d 13/04; F16h 1/44 US. Cl. 74-711 35 Claims Matter enclosedin heavy brackets II] appears in the original patent hut forms no partof this reissue specification; matter printed in italics indicates theadditions made by reissue.

ABSTRACT OF THE DISCLOSURE A limited slip differential mechanism havinga normally disengaged main clutch producing lock-up when activated,which is operated by means of an actuator device in turn activated by apredetermined level of differential action which is varied with the rateof change of levels of differential action. The actuator includes anactuator member which is rotationally driven by differential action andupon which spring-biased centrifugal weights are pivotally mounted andarranged so that at a predetermined velocity and acceleration of theactuator member one of the weights move outwardly and applies a brakingforce to the actuator member inhibiting its rotation. An arrangement isprovided for actuation of the normally disengaged main clutch inresponse to this inhibited rotation, so that the differential action isuninhibited at low levels of differential action. A high road speedcutout of the actuator is also provided so that no lock-up will occur atrelatively high road speeds.

BACKGROUND OF THE INVENTION This invention is related to limited slipdifferentials and more particularly to such differentials in which theslip inhibiting mechanism is wholly inoperative until predeterminedlevels of differential action and rate of change of differential actionare reached.

Prior art limited slip differentials have for the most part includedmechanisms which produce an inhibiting action on the differential at alllevels of differentiation. While this arrangement is satisfactory fromthe standpoint of vehicle stability on dry pavement since the inhibitingforce levels produced during normal turning operations is low enough tohave a negligible effect on the vehicle stability, on slippery roadsthis inhibiting action can produce vehicle instability during turningmaneuvers. Furthermore, even on dry pavement tire wear is increased dueto the scrubbing action during turns.

Some prior art limited slip differentials have attempted to solve thisproblem by providing a lock-up clutch which remain totally unengageduntil a predetermined level of differential action occurs, and then isengaged at that point. However, the actuation means has relied onviscous or frictional forces, and tends to be unreliable throughextremes of temperature and Wear. Other devices would produce suddenapplications of the clutch, producing a harsh shock upon lock-up.

Hence, it is an object of the present invention to provide an improvedlimited slip differential in which low levels of differential action arewholly uninhibited, but which locks up under conditions of high levelsof differential action and rates of change of differential action,indicating a wheel spin condition.

It is a further object to provide a limited slip differential in whichthe point of lock-up is reliably and accurately controlled.

ice

Another object of the present invention is to provide a centrifugalactuator suitable for use in this type of differential which produces asmooth clutch actuation reliably and accurately.

SUMMARY These and other objects which will become apparent upon areading of the following detailed description and the appended claimsare accomplished by providing a member which is rotationally driven bythe differential action, and which is arranged to actuate a lock-upclutch upon attaining a predetermined angular velocity and acceleration,indicating a wheel spin condition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view in partialsection of a differential incorporating an actuator according to thepresent invention.

FIG. 2 is a view of the section taken along the line IIII in FIG. 1.

FIG. 3 is a detail in partial section of the actuator shown in FIG. 1.

FIG. 4 is a detail view of the actuator showing the assembly of thecentrifugal weights.

FIG. 5 is a view of the section taken along the line VV in FIG. 3.

FIG. 6 is a schematic view of the weights acting under the forcesproduces by angular acceleration and velocity of the actuator assemblyin the counterclockwise direction.

FIG. 7 is a schematic view of the weights acting under the forcesproduced by angular acceleration and velocity of the actuator in theclockwise direction.

FIG. 8 is a partial view of a differential using an alternate type ofclutch operated by an actuator according to the present invention.

FIG. 9 is a view of the section taken along the lines IX-IX in FIG. 8.

FIG. 10 is a partial view of a differential using another alternatelock-up clutch operated by an actuator according to the presentinvention.

DETAILED DESCRIPTION Referring now to the drawings and particularly toFIG. 1, 10 indicates a planetary differential mechanism having an inputring gear 12 secured to a differential carrier housing 14. Rotatablysupported therein are a pair of side gears 16 and 18, splined to theaxles 20 and 22, which mesh with the planet pinions 24 and 26 (FIG. 2).The planet pinions 24 and 26 are rotatably mounted to shaft 28 which isin turn secured to the carrier housing 14.

In order to lock up the differential 10 a clutch mechanism 30 isprovided, which will act when actuated to clutch together the side gear16 and the carrier housing 14 to lock up the differential. This clutch30 is com prised of a double coned wedging member 32, cooperating with apocket 34 formed in the carrier housing 14. The wedging member 32 isdrivingly connected to the side gear 16 via wedging ramp surfaces 36 and38 formed in the Wedge member 32 and side gear respectively. These rampsurfaces will serve to actuate the clutch when relative rotativemovement between the side gear 16 and the wedge 32 is induced in amanner to hereinafter be described.

Biasing of the wedge 32 to the right opposing actuation in FIG. 1 isaccomplished by retainer 40 pressed onto side gear 16 and wave spring 42engaging the retainer 40 and the wedge 32.

Rotatably mounted in the carrier housing 14 is a centrifugal actuatorassembly 44. This actuator is provided with a pin 46 having integral atone end a pinion gear 50 drivingly engaging the wedge 32 via teeth 48formed about it periphery. Supported on the pin 46 are a pair ofcentrifugal weights 52 and 54 surrounding a drive spring 56. Drivespring 56 is compressed between shoulders 58 and 60, connected to pin46, so as to create a frictional drive therebetween. This drive istransmitted to the weights 52 and 54 via end sections 62 and 64 (FIGS. 1and of the drive spring 56 inserted into split pin 66 which serves topivotally connect the weights 52 and 54. This drive connection alsoserves to locate the connected weights 52 and 54 with respect to the pin46.

Weights 52 and 54 are spring loaded inwardly by means of a spring 68(FIG. 4) mounted on split pivot pin 66, so that in the absence ofcentrifugal force they assume the position shown in FIGS. 2 and 5.

Pivotally mounted to the carrier housing 14 is a stop assembly 70 (FIG.2) which includes a tab member 72 pivotally mounted via pin 74 to thecarrier housing 14, and is located in the position shown in FIG. 2 bymeans of a spring 76 tending to bias the tab member in a clockwisedirection as viewed in FIG. 2 and by means of a stop tab 78 (FIGS. 1, 2)cooperating with a shoulder 80 formed on the opening 81 in the carrierhousing which accommodates the actuator assembly 44.

Tab member 72 is provided with a pair of stop tabs 82, 84 designed tocooperate with end notches 86, 88 formed in the ends of weights 54, 56when the weights are extended away from the pin 46 due to centrifugaland inertia forces, as will hereinafter be described more fully.

Fixed to tab member 72 is a weight 90 which is positioned so thatrotation of the carrier housing 14 produces centrifugal force tending torotate the tab member 72 about pin 74 against spring 76 so as to movestop tabs 82, 84 away from the weights 52, 54.

OPERATION From the above description it should be clear that unless thecltuch 30 is engaged, normal differential action will occur, whollyuninhibited, since no lock-up forces exist until the time of clutchengagement except for the frictional and inertia forces in actuatormechanism 44, and the other driven parts. Wavespring 42 insures that thewedge member 32 will not be forced over by the ramps 36, 38 reaching tothe inertia of the wedge member 32 nor the inertia or friction forcescreated by the actuator assembly 44 which is driven by the wedge 32during differential action.

When differential action has reached a predetermined level, indicating awheel spin condition, the angular velocity and acceleration of the pin46 and carried weights 52, 54 will be sufiicient to cause one or theother of these weights to move away from the pin 46 and drive spring 56against the bias of spring 68 and to engage either one or the other ofthe stop tabs 82, 84. As shown in FIGS. 6 and 7, the forces acting onthe weights 52, 54 are such that the proper weight will move outwardlydepending on the direction of rotation of the pin 46, which will bedriven in one direction or the other, depending on which wheel isovertraveling the other. If the assembly is spinning counterclockwise,the inertia force, F;, of the weight 54 will be tending to open theweight, i.e., to move it away from pin 46 and drive spring 56, while theinertia force F, of weight 52 will be tending to hold it closed. Hence,when the centrifugal force F combined with the inertia force on weight54 reaches sufficient level to overcome spring 68, this weight will moveout to engage stop tab 82.

It should be emphasized that the responsiveness of the weights to bothvelocity and acceleration provides a superior wheel spin indicator sinceaccelerator levels are generally much higher in a wheel spin conditionthan during a turning maneuver for a given level of differential action.Hence, under conditions of rapidly changing differentiation, the pointof clutch lock-up will occur at lower levels of differential action thanunder conditions of slow changing differentiation, thus yielding a moreaccurate and reliable lock-up action: This responsiveness toacceleration is of course dependent on the drive ratios of the pin 46 tothe wedge member, the geometry of the drive connection with the weights,the mass of the weights, the bias of the springs 68, etc.

Since both weights 52, 54 are biased by the same spring 68, weight 52 isfurther held inward by the increased tension of the spring 68 when theweight 54 moves outwardly and tends to keep weight 52 held inwardregardless of the level of centrifugal or inertial forces developed.

As shown in FIG. 7, the reverse is true upon clockwise rotation of thepin 46.

Hence, the proper weight to engage the properly directed stop tab 82 or84 will move outwardly first.

Upon engagement of one of these weights 52, 54 with a respective tab 84,82, a braking force will be developed tending to restrict rotation ofpin 46 about its own axis. While weights 52, 54 are positively brakedfrom further movement, pin 46 is acted on through the frictionalconnection of the drive spring 56 acting on the shoulders 58 and 60,which limits the amount of braking torque acting on the pin 46.

This braking force acts as a retarding force on wedge member 32 byvirtue of the drive connection of the gear teeth 48, 50. This retardingforce in turn activates the ramps 36, 38 and causes the wedge member 32to overcome the bias of wavespring 42 and move to engage the coneportion 32 with the pocket 34, and once in contact, the self energizingaction of the cones fully engages the clutch, thus locking up thedifferential and precluding further differential action.

This lock-up is accomplished smoothly and without grahing or chattersince the retarding force is limited by the torque limiting drive of thedrive spring 56. In addition, it can be seen that differential action iscompletely uninhibited at low levels of differential action, whilecompletely precluded at higher levels due to the discrete actuationcharacteristics of the clutch actuation mechanism.

Upon an increase in road speed sufficient for the bias of spring 76 tobe overcome by the centrifugal force of the weight 90, tab member 72rotates about pin 74 so as to move tab stop portions 82, 84 out of reachof the weights 52, 54 in their extended position. Hence, thedifferential locking mechanism will be nullified at high road speeds,serving to retain vehicle control upon encountering slippery patches ofroad at these relatively high road speeds.

Upon the cessation of differential action and the reversal of drivebetween ramps 36, 38, wavespring 42 will disengage clutch mechanism 30.

An alternate embodiment is shown in FIGS. 8 and 9, in which a frictiondisc clutch is substituted for the cone clutch of the embodiment ofFIGS. 17. In this embodiment, the centrifugal actuation mechanism 44 isthe same, having a pin 46 and pinion gear 50 drivingly engaging a wedgemember 32. Upon energization of the centrifugal actuation mechanism 44the wedge member 32 is driven by the ramps 36, 38 to cause the frictiondiscs 92, 94 which are keyed to the side gear 16 and carrier housing 14respectively to be clutched together and to lock up the differential.Since the first friction disc 94 encountered is keyed to the carrierhousing 14 and the wedge member 32 is drivingly connected to the side 16via ramps 36, 38, a self energization effect is obtained by thedifferential speed between those elements reacting with the ramps 36,38. As shown in FIG. 9, the compression of the discs 92, 94 by the wedgemember 32 is limited by a projection 98 cooperating with an opening 96serving to limit rotative movement between the side gear 16 and thewedge member 32, and hence limit linear travel of the wedge memher 32.An actuation reaction is provided by Belleville back-up spring 100.

Another embodiment is shown in FIG. 10. in which a roller clutch issubstituted for the cone clutch 30 shown in the embodiment of FIGS. 1-7.In this embodiment a roller clutch of the type having a series ofrollers 104 and cage member 102 which controls their locking action iscontrolled by the actuation mechanism 44 according to the presentinvention. This is accomplished by providing a geared connection withthe pinion 50 and the cage 102. As is described in US. Pats. 3,324,744and 3,448,636 which may be referred to for a more complete descriptionof the roller clutch, differential action is uninhibited as long as thecage 102 is free to rotate with respect to carrier housing 14, but uponthe development of a significant drag force therebetween, the rollerslock together the carrier housing 14 and the side gear 16, and henceeliminate further differential action. This retarding force is providedaccording to the present invention by the centrifugal actuationmethanism 44 acting through pinion 50.

From the above detailed description it will be appreciated that asimple, reliable mechanism has been provided to actuate a lock-up clutchin a differential so as to have wholly uninhibited differential actionat low speeds, a smooth lock-up levels and rates of change of levels ofdifferential action indicating wheel spin, and a nullification of thelock-up mechanism at high road speeds, all cooperating to retain maximumvehicle stability and control, while obtaining excellent tractiveability on slippery drive surfaces.

It is understood that the invention may be practiced in a variety offorms, substituting equivalents for the various elements described.

I claim:

1. In a planetary differential having a plurality of driving membersincluding an input and two output members the improvement comprising:

an actuator member;

driving means driving said actuator member in response to differentialmovement of said members;

a clutch mechanism normally disengaged operable to lock up saiddifferential;

actuation means producing actuation of said clutch mechanism by saidactuator member in response to a predetermined drive level of saidactuator member, including means creating a [locking] retarding force onsaid actuator member and means responsive to the application of aretarding force to said actuator member for actuating said clutch means,whereby said differential is locked up when a predetermined level ofdifferential action occurs.

2. The differential of claim 1 wherein said actuation means furtherincludes means producing said actuation of said clutch mechanism atpredetermined drive levels of said actuator member varying with theacceleration of said actuator member, whereby said predetermined levelof differential action causing lock-up varies as the rate of change ofdifferential action changes.

3. The differential of claim 1 wherein said actuation means furtherincludes means limiting the [locking] retarding force applied to saidactuator member in response to said predetermined drive level.

4. The differential of claim 1 wherein said [locking] retarding meansincludes at least one element driven by said actuator and means forpositively locking said at least one element against said drive to[said] one of said [other] driving members in response to saidpredetermined drive level and further including force limiting meansbetween said element and said actuator member to limit the [locking]retarding force transmitted thereby.

5. The differential of claim 4 wherein said clutch mechanism includes anengagement element driven by another of said [differential elements]driving members and said driving means includes means providing adriving connection between said engagement element and said actuatormember [and also includes means actuating said clutch mechanism inresponse to said locking force acting on said actuating member].

6. The differential of claim 5 wherein said [actuating] means responsiveto application of a retarding force includes a wedging connectionbetween said engagement member and said [another differential] otherdriving member.

7. The differential of claim 1 wherein said actuator member is rotatablydriven in response to said differential movement by said driving means.

8. The differential of claim 7 wherein said actuation means alsoincludes means varying said predetermined drive level as a function ofthe angular acceleration of said actuator member.

9. The differential of claim 7 wherein said driving means includes meansrotatably mounting said actuator member on one of said [differential]driving members and also includes means providing a driving connectionbetween said actuator member and another of said [differential] drivingmembers.

10. The differential of claim 9 wherein said actuation means includesbrake means producing a [locking] retarding force on said actuatormember tending to prevent said rotation in response to saidpredetermined level of differential movement.

11. The differential of claim 10 wherein said brake means includes atleast one element driven by said actuator member and also includeslocking means locking said at least one element to said one[differential] driving member in response to said predetermineddifferential movement.

12. The differential of claim 11 wherein said brake means also includesa torque limiting drive connection between said at least one element andsaid actuator member.

13. The differential of claim 12 wherein said locking means includesmeans mounting said at least one element so as to be capable of movementin response to centrifugal force generated by said rotation and furtherincludes stop means on said [another] one of said [differential] drivingmembers mounted to engage said at least one element in a position of itstravel in response to said centrifugal force and also includes meanscontrolling said movement so as to cause said at least one element toengage said stop means at a rotational speed corresponding to saidpredetermined level of differential movement.

14. The differential of claim 13 wherein said means mounting said atleast one element includes means influencing said movement by inertialforces created by acceleration of said at least one element.

15. The differential of claim 13 wherein said means controlling saidmovement includes resilient bias means resiliently biasing said at leastone element against movement in response to said rotational movement.

16. The differential of claim 13 wherein said braking means includes apair of elements driven by said actuator member and wherein said stopmeans includes a pair of stop portions engageable with a respectiveelement in a position of its travel in response to said centrifugalforce and also includes means controlling the relative response of saidelements to said centrifugal force so as to cause one of said elementsto move to engage a respective stop portion, before the other of saidelements moves to engage said stop portions in one direction of rotationof said actuator member and to cause said other element to move toengage the other stop portion in response to said rotation in the otherdirection before said one element moves to engage its respective stopportion, and further includes means preventing the one or the otherelement from moving to engage said stop portion when the other of eitherof said one or the other element has moved to engage said stop portion.

17. The differential of claim 13 further including null means nullifyingsaid stop means upon reaching a predetermined speed of said [inputmember] one of said driving members of said differential, whereby saidactuating means is prevented from actuating said clutch at speeds inexcess of said predetermined speed of said input element.

18. The differential of claim 17 wherein said null means includes aweight mounted to respond to centrifugal force generated by rotation ofsaid [input member] one of said driving members and also includes meanspreventing said stop means from engaging said at least one element inresponse to movement of said weight corresponding to said predeterminedspeed of said input element.

19. A centrifugal actuator comprising:

a drive element;

a pair of weights;

means rotatably mounting said weights with respect to said drive elementso as to allow rotation away from said drive element;

means drivingly connecting said weights and said drive element [as] soas to cause said weights to rotate with said drive element and includinga connection therebetween which creates inertia forces tending to rotatethe weights in directions tending to move one weight toward and theother way from said drive member in response to angular acceleration ofsaid drive element in one direction and tending to move said weights inthe opposite relative direction in response to acceleration of saiddrive member in the other direction; means engaging said weights upon apredetermined travel away from said drive element, including a pair ofstop portions adapted to engage a respective [weight] one of saidweights to retard rotation of said drive element;

means biasing said weights inwardly, whereby the inertia forces createdby said drive connection causes one or the other of said weights toengage a respective stop portion [first] depending on the direction ofrotation in response to increasing angular velocity of said driveelement.

20. The actuator of claim 19 wherein said means mounting said weightsincludes a common pivotal connection away from the center of gravity ofsaid weights, and wherein said drive connection includes an armdrivingly connected to said drive element and to said pivotalconnection, whereby said weights respond to both centrifugal andinertial forces.

21. The actuator of claim 19 wherein said means drivingly connectingsaid weights and said drive element includes a torque limit meanslimiting the torque transmitted therebetween.

22. A limited slip differential comprising:

a carrier housing;

a first and second side gears rotatably mounted in said carrier housing;

a plurality of planet pinions, rotatably mounted by said carrierhousing, meshing with said first and second side gears;

clutch means for connecting said carrier housing and one of said sidegears, including an engagement member carried by said one side gear,having cooperating surfaces therebetween to cause axial movement of saidengagement member in response to relative rotative movement therebetweenand also including means actuating said clutch means upon continuedaxial movement of said engagement member;

an actuator member, rotatably supported by said carrier housing;

means drivingly connecting said engagement member and said actuatormember so as to cause rotation of said actuator member in response torelative rotation of said carrier housing and said engagement member;means for braking said actuator member against said rotation in responseto said actuator member attaining a predetermined angular velocity,whereby said engagement member is rotationally displaced relative saidside gear in response to a predetermined level of differential action,thereby causing said clutch means to lock up said differential.

23. The differential of claim 22 wherein said braking means includesmeans varying said predetermined angular velocity responded to as atfunction of angular acceleration of said member.

24. The differential of claim 22 wherein said means drivingly connectingsaid actuator member and said engagement member is a geared connectiontherebetween.

25. The differential of claim 22 wherein said clutch means furtherincludes a double coned portion connected to said engagement member anda cooperating pocket formed in said carrier housing and positioned toengage said double coned portion upon said continued axial movement ofsaid engagement member.

26. The differential of claim 22 wherein said braking means includes apair of weights mounted on said actuator member and drivingly connectedthereto, and also includes means causing one or the other of saidweights depending on the direction of rotation of said weights to moveoutwardly in response to the attainment of said angular velocity andalso includes locking means creating a braking force on said actuatormember in response to said movement of either of said weights.

27. The differential of claim 26 wherein said locking means includesmeans locking said weights to said carrier housing in response to theattainment of said angular velocity by said actuator member and whereinsaid driving connection between said actuator member and said weightsincludes a torque limiting means whereby the braking force exerted bysaid weights upon locking engagement with said carrier housing islimited to produce smooth engagement of said clutch means.

28. In a planetary differential having a plurality of driving membersincluding an input and two output members the improvement comprising:

an actuator member;

driving means driving said actuator member in response to differentialmovement of said members;

a. clutch mechanism operable to connect together the driving members ofsaid differential;

actuation means producing actuation of said clutch mechanism by saidactuator member in response to a predetermined drive level of saidactuator member including means varying the predetermined drive levelresponded to as a function of the acceleration of said actuator member,whereby said driving members are connected together when a predeterminedlevel of differential action occurs, varying as a function of the rateof change of differential action.

29 In a drive mechanism:

relatively rotatable driving and driven members;

clutch means located between said members and operable between a firstcondition wherein said members are capable of rotating relative to eachother and a second condition operatively interconnecting said members toretard relative rotation between said members;

an actuator member for effecting operation of said clutch means to saidsecond condition;

driving means driving said actuator member in response to relativerotation of said members;

actuation means producing actuation of said clutch means by saidactuator member in response to a predetermined drive level of saidactuator member, including means creating a locking force on saidactuator member and means responsive to the application of a lockingforce to said actuator member for actuating said clutch means wherebysaid members are locked up when a predetermined level of relativerotation occurs therebetween.

30. In a drive mechanism:

a driving member;

a driven member;

clutch means located between said members and operable upon axialloading thereof to retard relative rotation of said members;

said clutch means including an engagement member carried by one of saidmembers;

said one of said members, and said engagement member having cooperatingsurfaces effecting axial loading of said clutch means in response torelative rotative movement therebetween;

an actuator member rotatably supported by the other of said members;

means for driving said actuator member in response to relative rotationbetween said members;

means for braking said actuator member against said rotation in responseto said actuator member [attainin] attaining a predetermined angularvelocity;

said actuator member and engagement member having cooperating portionseffecting relative rotation of said engagement member relative to saidone of said members upon braking of said actuator member to therebyeffect axial loading of said clutch means and retardation of relativerotation between said members.

31. A centrifugal actuator comprising:

a drive element;

weight means;

means rotatably mounting said weight means with respect to said driveelement so as to allow for rotation thereof away from said driveelement;

means drivingly connecting said weight means and said drive element soas to cause said weight means to rotate with said drive element andincluding a connection therebetween which creates inertia forces tendingto rotate the weight means in directions tending to move at least aportion of said weight means toward and another portion of said weightmeans away from said drive element in response to an angularacceleration of said drive element in one direction and tending to movesaid portions of said weight means in opposite relative directions inresponse to [acceleraton] acceleration of said drive element in theother direction;

means engaging said weight means upon a predetermined travel away fromdrive element including stop portions adapted to engage the respectiveportions of said weight means;

means biasing said weight means inwardly whereby the inertia forcescreated by said drive connection causes one or the other of saidportions of said weight means to engage a respective stop portion firstdepending on the direction of rotation in response to increasing angularvelocity of said drive element.

32. A differential drive assembly comprising.

an input member,

a rotatable output member,

difierential gear means for drivingly connecting said input member withsaid output member and for enabling relative rotation to occur betweensaid input and output members,

clutch means operable from a disengaged condition to an engagedcondition to retard relative rotation between said input and outputmembers, and

actuator means for eflecting operation of said clutch means to theengaged condition in response to a predetermined rate of relativerotation between said input and output members, said actuator meansincluding an actuator member, drive means for moving said actuatormember at a rate which varies as a function of variations in the speedof relative rotation between said input and output members, means fordeveloping a force which is efiective to retard movement of saidactuator member at least when the predetermined speed of relativerotation is present be. tween said input and output members, and meansfor efiecting operation of said clutch means to the engaged condition inresponse to retardation of movement of said actuator member.

33. A differential drive assembly as set forth in claim 32 furtherincluding means for supporting said actuator member for rotation aboutits central axis, said drive means being eflective to rotate saidactuator member about its central axis at a speed which varies as afunction of variations in the speed of relative rotation between saidinput and output members.

34. A differential drive assembly as set forth in claim 32 furtherincluding means for rendering said actuator means inefiective to efiectoperation of said clutch means in response to rotation of said inputmember at a speed which is greater than a predetermined speed.

35. A difierential drive assembly as set forth in claim 32 wherein saidinput member includes a carrier, said actuator member being disposed onsaid carrier for movement therewith, said differential gear meansincludes a side gear and a pinion gear, said clutch means includes afirst clutch surface connected with said carrier and a second clutchsurface connected with said side gear, said drive means including meansconnected with said second clutch surface and said side gear forefiecting movement of said actuator member at a rate which varies as afunction of the rate of relative rotation between said carrier and sidegear, said means for effecting operation of said clutch means to theengaged condition including means for urging said first and secondclutch surfaces toward each other.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,550,750 5/1951 Abelt 74-711 2,720,796 10/1955Schou 74-711 3,448,636 6/1969 Roper et a1. 7471l 3,517,573 6/ 1970 Roper74-711 FOREIGN PATENTS 183,712 8/1922 Great Britain 747 11 583,974l/1947 Great Britain 74-71 1 1,103,795 2/1968 Great Britain 192-103 CARTHUR T. MCKEON, Primary Examiner US. Cl. X.R. 192-35

